[ovs-dev] [PATCH 5/5] [RFC] ofp-actions: Check pre-requisists of set-field actions

[Ben Pfaff]

On Wed, Sep 12, 2012 at 05:44:32PM +0900, Simon Horman wrote:
> By passing a flow to the action parser the pre-requisites
> of set-feild actions will be checked. If the flow is NULL,
> for instance in test code such as ofctl_parse_ofp11_instructions(),
> then the check is skiped, as it always was before this change.
> 
> Unfortunately I don't think that this check is correct as
> it does not take into account other actions actions that may
> be applied before the load action, e.g. vlan push/pop, which may
> affect the pre-requisites.
> 
> I believe that in its current form there is scope for both false positives
> (not so bad, perhaps) and false negatives (pretty bad). I would welcome
> some input on if these concerns are valid and if so how they may be
> overcome.

When I've thought about this problem before, I wasn't able to come up
with an example of when the prerequisite check would be wrong.  Do you
have an example?

Thanks,

Ben.